Surface chemistry of In 2O 3 deposition using In(CH 3) 3 and H 2O in a binary reaction sequence

Abstract

Sequential surface chemical reactions for the controlled deposition of In 2O 3 were examined using transmission Fourier transform infrared (FTIR) spectroscopy. In this study, the binary reaction (2In(CH 3) 3+3H 2O→In 2O 3+6CH 4) was separated into two half-reactions: (A) InOH ∗+In(CH 3) 3→In–O–In(CH 3) ∗ 2+CH 4 ; (B) InCH ∗ 3+H 2O→InOH ∗+CH 4 , where the asterisks designate the surface species. The InOH * and InCH 3 * surface species were monitored by the infrared absorbances of the InO–H and InC–H 3 stretching vibrations. The reactions were thermally activated and the maximum reaction temperature was limited to 525 K because of trimethylindium (TMIn) pyrolysis. At 525 K, the (A) reaction saturated after depletion of ∼60% of the InOH * coverage. In contrast, the (B) reaction went to completion and was self-limiting. Despite these observed surface reactions, the growth of conformal In 2O 3 films was not achieved on Si(100) at 525 K. Very rough In 2O 3 films with low growth rates were also observed at 675–775 K in previous studies using InCl 3 and H 2O in a binary reaction sequence. The thermal stabilities of the InOH * and InCH 3 * surface species were measured from 300–900 K. The low coverage of surface species at the various reaction temperatures may explain the rough In 2O 3 films and low In 2O 3 growth rates.